There are many situations where the safety of a patient requires monitoring the movement of the patient within a hospital or other type of patient facility. Typically, the patient is unable to protect themselves and provide for their own safety. For example, individuals suffering from some form of mental illness may require hospitalization for a variety of reasons. Such individuals are usually unrestrained. However, there is a concern that the individual may attempt to leave the facility or enter an area which may be hazardous to their well-being or the well-being of others. As a further example, it is unfortunately necessary to protect newborns and infants from being kidnapped. In addition to the safety and security of a patient, such entities, and the individuals managing such entities, have a responsibility to provide for the reasonable protection of patients under their care.
Security personnel are often employed to assure that individuals leaving or entering the premises are authorized to do so. Typically, the entrance and exists of facilities are staffed with security personnel. Hallways and other locations may also be patrolled by security personnel. In addition, video cameras may be strategically located throughout the facility and provide a video feed to a central monitoring system. The central monitoring system may be monitored by security personnel or other staff members.
It is also known to secure tags to individuals. U.S. Pat. No. 4,885,571 (PAULEY et al.) discloses a tag for use with a system for monitoring an individual. Two capacitive electrodes, one of which is realized as a conductive strap that attaches the tag to the individual and the other as a plate within the tag itself, function as the plates of capacitor, with the body flesh serving as the dielectric material therebetween. An oscillator signal is applied to strap and is received by the tag plate through the body flesh. A switch is connected to the tag plate. The switch is activated as long as the body remains between the strap and the tag plate. If the strap is removed, however, the switch is not activated and a tamper signal is sent to encoding circuitry. The encoding circuitry works with other tag circuits so that an identification signal is periodically transmitted. This signal includes information such as an indication that the tag has been removed from the individual.
U.S. Pat. No. 5,541,580 (GERSTON et al.) shows a tag for detecting a body. The device uses a plate in a tag as a first electrode and, as a second electrode, a strap that holds the tag to the wearer's wrist or ankle. The wearer's wrist of ankle serves as the dielectric between the two electrodes so that a capacitor is formed. See item 20 in FIG. 1. The capacitance of this capacitor is measured to establish a range of acceptable values. The range of acceptable values are based upon the theory that slowly occurring and minor capacitance changes are normal while illegitimate activities, such as complete removal of the tag, result in rapid and large capacitance changes. As described in col. 5, lines 56-67 and col. 6, line 1, the circuit of FIG. 4 may be used to make required measurements. More specifically, as shown in FIG. 4, the capacitor 20 is connected to a signal generator 60 that includes an inverting circuit 62 with a resistor 64 coupling between the input and output thereof. As a result, signal generator 60 produces a signal that oscillates at a frequency that varies in response to the capacitance of capacitor 20 and the dielectric constant in region 26 (FIG. 1).
U.S. Pat. No. 4,293,852 (ROGERS) shows a capacitive article removal alarm capable of detecting when an article is removed from a predetermined position. The device is particularly suited for use in the prevention of shoplifting. The protected article is either metallic, incorporates metal near its base or carries a sticker tag that incorporates metal. The article is positioned so as to overlie a pair of electrode strips which communicate with a sensing circuit. The sensing circuit features an oscillator and is configured to go into and out of oscillation by the change of capacity occurring between the electrode strips. The sensing circuit also features a variable capacitor that is adjusted so that the oscillator is just not oscillating when the protected article is placed in position. As a result, when the article is removed from its position, the capacitance across the electrode strips decreases and the oscillator starts working. An alarm circuit receives the oscillating output from the sensor circuit and triggers an alarm such as a bell.
There are various problems and deficiencies in the prior art tags. For instance, the prior art does not disclose a tag which provides satisfactory isolation between the individual and the electrical circuit. In addition, the prior art tags have large current requirements. The prior art tags also have a short useful life without maintenance.